Support compound assignment for native integers.

ICSharpCode.Decompiler.Tests/TestCases/Correctness/CompoundAssignment.cs

@@ -32,6 +32,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			UnsignedShiftRightStaticProperty();
 			DivideByBigValue();
 			Overflow();
+			IntPtr_CompoundAssign();
 		}
 
 		static void Test(int a, int b)
@@ -104,6 +105,19 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			}
 		}
 
+		IntPtr intPtrField = new IntPtr(IntPtr.Size == 8 ? long.MaxValue : int.MaxValue);
+
+		public IntPtr IntPtrProperty {
+			get {
+				Console.WriteLine("In {0}.get_IntPtrProperty", instanceNumber);
+				return intPtrField;
+			}
+			set {
+				Console.WriteLine("In {0}.set_IntPtrProperty, value={1}", instanceNumber, value);
+				intPtrField = value;
+			}
+		}
+
 		public static Dictionary<string, int> GetDict()
 		{
 			Console.WriteLine("In GetDict()");
@@ -112,8 +126,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 
 		static CompoundAssignment GetObject()
 		{
-			Console.WriteLine("In GetObject() (instance #)");
+			var obj = new CompoundAssignment();
-			return new CompoundAssignment();
+			Console.WriteLine("In GetObject() (instance #{0})", obj.instanceNumber);
+			return obj;
 		}
 
 		static string GetString()
@@ -208,5 +223,14 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 		{
 			return val;
 		}
+
+		static void IntPtr_CompoundAssign()
+		{
+			Console.WriteLine("IntPtr_CompoundAssign:");
+#if !MCS
+			GetObject().IntPtrProperty -= 2;
+			GetObject().IntPtrProperty += 2;
+#endif
+		}
 	}
 }

ICSharpCode.Decompiler.Tests/TestCases/Pretty/NativeInts.cs

@@ -134,5 +134,32 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				(nint)i64
 			};
 		}
+
+		public NativeInts GetInstance(int i)
+		{
+			return this;
+		}
+
+		public void CompoundAssign()
+		{
+			GetInstance(0).i += i32;
+			checked {
+				GetInstance(1).i += i32;
+			}
+			GetInstance(2).u *= 2u;
+			checked {
+				GetInstance(3).u *= 2u;
+			}
+			GetInstance(4).intptr += (nint)i32;
+			checked {
+				// Note: the cast is necessary here, without it we'd call IntPtr.op_Addition
+				// but that is always unchecked.
+				GetInstance(5).intptr += (nint)i32;
+			}
+			// multiplication results in compiler-error without the cast
+			GetInstance(6).intptr *= (nint)2;
+
+			GetInstance(7).i <<= i32;
+		}
 	}
 }

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1577,10 +1577,7 @@ namespace ICSharpCode.Decompiler.CSharp
 							}
 						} else {
 							IType targetType = NullableType.GetUnderlyingType(target.Type).GetEnumUnderlyingType();
-							if (NullableType.IsNullable(value.Type)) {
+							value = ConvertValue(value, targetType);
-								targetType = NullableType.Create(compilation, targetType);
-							}
-							value = value.ConvertTo(targetType, this, inst.CheckForOverflow, allowImplicitConversion: true);
 						}
 						break;
 					case AssignmentOperatorType.Multiply:
@@ -1590,10 +1587,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					case AssignmentOperatorType.BitwiseOr:
 					case AssignmentOperatorType.ExclusiveOr: {
 							IType targetType = NullableType.GetUnderlyingType(target.Type);
-							if (NullableType.IsNullable(value.Type)) {
+							value = ConvertValue(value, targetType);
-								targetType = NullableType.Create(compilation, targetType);
-							}
-							value = value.ConvertTo(targetType, this, inst.CheckForOverflow, allowImplicitConversion: true);
 							break;
 						}
 				}
@@ -1605,6 +1599,20 @@ namespace ICSharpCode.Decompiler.CSharp
 				resultExpr.Expression.AddAnnotation(inst.CheckForOverflow ? AddCheckedBlocks.CheckedAnnotation : AddCheckedBlocks.UncheckedAnnotation);
 			}
 			return resultExpr;
+
+			TranslatedExpression ConvertValue(TranslatedExpression value, IType targetType)
+			{
+				bool allowImplicitConversion = true;
+				if (targetType.GetStackType() == StackType.I) {
+					// Force explicit cast for (U)IntPtr, keep allowing implicit conversion only for n(u)int
+					allowImplicitConversion = targetType.IsCSharpNativeIntegerType();
+					targetType = targetType.GetSign() == Sign.Unsigned ? SpecialType.NUInt : SpecialType.NInt;
+				}
+				if (NullableType.IsNullable(value.Type)) {
+					targetType = NullableType.Create(compilation, targetType);
+				}
+				return value.ConvertTo(targetType, this, inst.CheckForOverflow, allowImplicitConversion);
+			}
 		}
 		
 		TranslatedExpression HandleCompoundShift(NumericCompoundAssign inst, AssignmentOperatorType op)

ICSharpCode.Decompiler/IL/Instructions/CompoundAssignmentInstruction.cs

@@ -151,7 +151,7 @@ namespace ICSharpCode.Decompiler.IL
 			CompoundTargetKind targetKind, ILInstruction value, IType type, CompoundEvalMode evalMode)
 			: base(OpCode.NumericCompoundAssign, evalMode, target, targetKind, value)
 		{
-			Debug.Assert(IsBinaryCompatibleWithType(binary, type));
+			Debug.Assert(IsBinaryCompatibleWithType(binary, type, null));
 			this.CheckForOverflow = binary.CheckForOverflow;
 			this.Sign = binary.Sign;
 			this.LeftInputType = binary.LeftInputType;
@@ -168,7 +168,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// <summary>
 		/// Gets whether the specific binary instruction is compatible with a compound operation on the specified type.
 		/// </summary>
-		internal static bool IsBinaryCompatibleWithType(BinaryNumericInstruction binary, IType type)
+		internal static bool IsBinaryCompatibleWithType(BinaryNumericInstruction binary, IType type, DecompilerSettings settings)
 		{
 			if (binary.IsLifted) {
 				if (!NullableType.IsNullable(type))
@@ -201,6 +201,19 @@ namespace ICSharpCode.Decompiler.IL
 					default:
 						return false; // operator not supported on pointer types
 				}
+			} else if (type.IsKnownType(KnownTypeCode.IntPtr) || type.IsKnownType(KnownTypeCode.UIntPtr)) {
+				// "target.intptr *= 2;" is compiler error, but
+				// "target.intptr *= (nint)2;" works
+				if (settings != null && !settings.NativeIntegers) {
+					// But if native integers are not available, we cannot use compound assignment.
+					return false;
+				}
+				// The trick with casting the RHS to n(u)int doesn't work for shifts:
+				switch (binary.Operator) {
+					case BinaryNumericOperator.ShiftLeft:
+					case BinaryNumericOperator.ShiftRight:
+						return false;
+				}
 			}
 			if (binary.Sign != Sign.None) {
 				if (type.IsCSharpSmallIntegerType()) {

ICSharpCode.Decompiler/IL/Transforms/TransformAssignment.cs

@@ -198,9 +198,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			}
 		}
 
-		static bool ValidateCompoundAssign(BinaryNumericInstruction binary, Conv conv, IType targetType)
+		static bool ValidateCompoundAssign(BinaryNumericInstruction binary, Conv conv, IType targetType, DecompilerSettings settings)
 		{
-			if (!NumericCompoundAssign.IsBinaryCompatibleWithType(binary, targetType))
+			if (!NumericCompoundAssign.IsBinaryCompatibleWithType(binary, targetType, settings))
 				return false;
 			if (conv != null && !(conv.TargetType == targetType.ToPrimitiveType() && conv.CheckForOverflow == binary.CheckForOverflow))
 				return false; // conv does not match binary operation
@@ -305,7 +305,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				}
 				if (!IsMatchingCompoundLoad(binary.Left, compoundStore, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: storeInSetter?.Variable))
 					return false;
-				if (!ValidateCompoundAssign(binary, smallIntConv, targetType))
+				if (!ValidateCompoundAssign(binary, smallIntConv, targetType, context.Settings))
 					return false;
 				context.Step($"Compound assignment (binary.numeric)", compoundStore);
 				finalizeMatch?.Invoke(context);
@@ -656,7 +656,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (binary != null && (binary.Right.MatchLdcI(1) || binary.Right.MatchLdcF4(1) || binary.Right.MatchLdcF8(1))) {
 				if (!(binary.Operator == BinaryNumericOperator.Add || binary.Operator == BinaryNumericOperator.Sub))
 					return false;
-				if (!ValidateCompoundAssign(binary, conv, targetType))
+				if (!ValidateCompoundAssign(binary, conv, targetType, context.Settings))
 					return false;
 				stloc = binary.Left as StLoc;
 			} else if (value is Call operatorCall && operatorCall.Method.IsOperator && operatorCall.Arguments.Count == 1) {
@@ -731,7 +731,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					return false;
 				if (!(binary.Operator == BinaryNumericOperator.Add || binary.Operator == BinaryNumericOperator.Sub))
 					return false;
-				if (!ValidateCompoundAssign(binary, conv, targetType))
+				if (!ValidateCompoundAssign(binary, conv, targetType, context.Settings))
 					return false;
 				context.Step("TransformPostIncDecOperator (builtin)", inst);
 				finalizeMatch?.Invoke(context);